1. Field of the Invention
The present invention relates to a projection type displaying apparatus and, more particularly, to a projection type displaying apparatus with a built-in screen, which is capable of projecting an image onto the built-in screen or onto an external separate screen.
2. Description of the Prior Art
Picture screens of home television receivers (hereafter, TV receivers) have recently been getting wider to display a finer and more detailed television picture, giving television watchers a more impressive picture. To meet the demand for a wider picture screen, projection type displaying apparatus (hereafter, projection apparatus) are widely used, which use, in place of a large sized cathode ray tube (CRT), a small sized CRT or a light bulb including a liquid crystal display device to project a television picture onto a wide screen.
Depending upon the system being used for projecting a picture onto a screen, the projection apparatus are classified into two types such as a front screen type projection apparatus and a rear screen type projection apparatus. In general, a size of a picture screen being set with little restriction, the front screen type projection apparatus is capable of displaying a larger sized television picture compared with the rear screen type projection apparatus. Meanwhile, the rear screen type projection apparatus has a structure substantially similar to conventional TV receivers and, therefore, has the advantage that is easier to manipulate as compared with the front screen type projection apparatus.
The conventional front screen type projection apparatus is a displaying apparatus which has a reflection type screen of a size, for example, from approximately 50-inch diagonal to 120-inch diagonal, and which projects a picture onto the reflection type screen from the front side thereof through an optical system. The rear screen type projection apparatus is a displaying apparatus which has a transmission type flat screen of a size, for example, from approximately 40-inch diagonal to 60-inch diagonal, and which projects a picture onto the transmission type flat screen from the rear side thereof through an optical system.
The conventional front screen type projection apparatus projects a picture onto the reflection type screen which is separately installed from the projection apparatus, and, therefore, a distance between a projection lens of the optical system and the reflection type screen can be set with little restriction. Therefore, in general, a wider picture size can be enjoyed in the front screen type projection apparatus than in the rear screen type projection apparatus.
Meanwhile, the rear screen type projection apparatus projects a picture onto a built-in screen, and, therefore, the distance between the projection lens of the optical system and the built-in screen has to be set within a predetermined distance range, which releases a user from a troublesome focus adjustment.
The conventional front screen type projection apparatus can project a wide sized picture, and the distance between the projection lens of the optical system and the screen can be set with little restriction. In other words, it is hard to set the distance in the front screen type projection apparatus and the focus of the projection lens has to be adjusted every time the projection apparatus is used. The front screen type projection apparatus has a drawback that the focus adjustment is troublesome.
Meanwhile, the conventional rear screen type projection apparatus enables easy focus adjustment, but has a limitation as to the size of the picture to be displayed. The rear screen type projection apparatus uses the built-in screen, and, therefore, the size of the built-in screen can not be made larger than a predetermined size, i.e., the size of the body of the projection apparatus. As described above, the rear screen type projection apparatus has a drawback that the size of a picture to be displayed can not be made wider than the body of the projection apparatus.
It would be apparent to those skilled in the art from the following description of preferred embodiments that the present invention may be modified in various manners and may be applicable to other apparatus.